Selenoglutathione (GSeH) is a water-soluble tripeptide, in which the sulfur atom of biologically important reductant glutathione (GSH) is replaced by a selenium atom, and exhibits a higher reducing activity than GSH. In this review, we overview the research on this selenium analogue of glutathione and look ahead to future research directions. Both solid-phase and liquid-phase methods can be used to chemically synthesize selenoglutathione diselenide (GSeSeG), the oxidized form of GSeH. Lesser amounts of GSeH are also found in the metabolic products of yeast and certain plants (garlic, sunflower sprouts, etc.) grown in a high-selenium medium. In the meantime, a biological method for the synthesis of GSeH using mutated yeast has recently been reported. Various applications of selenoglutathione in the field of biochemistry have already been explored. It has been reported that GSeSeG is an efficient catalyst for the oxidative folding of proteins. GSeSeG is also an excellent radical scavenger and potential detoxifier of intracellular xenobiotics. Recently, it has also been reported that GSeSeG has stress-reducing and antibacterial properties. Because GSeSeG has low toxicity, its unique reactivity is expected to be widely applied in the fields of applied biology and medicine.

Selenoprotein P (SeP) is the major selenium transport protein in the blood and plays a central role in selenium metabolism by being involved in selenoprotein synthesis via selenium supply in various tissues. On the other hand, excess selenoprotein P, which is increased in patients with diabetes and other diseases, can be a malignant protein that causes metabolic disorders in various tissues through disruption of redox homeostasis. Therefore, developing methods to control selenium metabolism in physiological and pathological conditions are significant. In this study, we focused on epigallocatechin gallate (EGCg), an electrophilic plant component, and newly found that modification of the cysteine residue in SeP by this molecule inhibits its cellular uptake in SH-SY5Ycells. SeP-EGCg adduct failed to induce the expression of glutathione peroxidase, which is synthesized in cells by selenium supply through SeP. These results suggest that EGCg can be a candidate molecule to induce negative remodeling of selenium metabolism by inhibiting SeP incorporation into the cells.